Massachusetts Institute of Technology, Cambridge, MA

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Stop Animal Exploitation NOW!
S. A. E. N.
"Exposing the truth to wipe out animal experimentation"

Government Grants Promoting Cruelty to Animals

Massachusetts Institute of Technology, Cambridge, MA

EARL K. MILLER - Primate Testing - 2006

Grant Number: 5R01MH065252-05
Project Title: Neural Basis of Categories
PI Information: PROFESSOR EARL K. MILLER, ekmiller@mit.edu 

Abstract: DESCRIPTION: (provided by applicant)
While much is understood about neural mechanisms that analyze the physical attributes of the visual environment, little is known about the culmination of these analyses: the assignment of categories that give stimuli meaning. Our group has developed a novel paradigm for studying visual categories. A morphing system is used to blend prototypes of "cats" and "dogs" into single images, with each image having a certain proportion of cat vs. dog. This allows us to continuously vary shape and precisely define a category boundary. Monkeys are trained to judge whether two successively presented images are from the same category. We recently found a neural correlate of category information in the prefrontal cortex (PFC): single neurons that show a sharp change in neural activity at the boundary between categories but relatively little differences in activity within a category. We now plan to use this paradigm to address fundamental questions about category representations. Using multiple electrode techniques, we will simultaneously record neural activity from the PFC and the inferior temporal cortex (TIC), a visual cortical area thought to be important for visual categories. This will allow us to directly compare and contrast their neural properties and relative timing and thus afford a precise assessment of the respective contributions to category-based behaviors. We will also test for category-coding in the hippocampus, a region that shares a close anatomical and functional relationship with the TIC and PFC. To explore whether categorization and identification have common neural substrates, we will record PFC and ITC activity while monkeys switch back and forth between categorizing stimuli and identifying individual category members. To determine if category-coding neurons are highly specialized (like "face cells"), we will test them with a wide range of real world stimuli. To determine whether multiple category memberships are represented by separate neural ensembles or instead multiplexed onto single neurons, we will record while monkeys switch between categorizing a set of stimuli under two different category schemes. Because categorization is central to cognition, data from this project has the potential to impact on a wide range of behaviors and human disorders. The ability to quickly glean concepts and meaning from experience is disrupted in a variety of neuro psychiatric disorders such as autism and schizophrenia. By identifying brain structures important for these abilities, discerning their relative roles, and uncovering their neural mechanisms, we can open a path to drug and behavioral therapies designed to alleviate their dysfunction.

Thesaurus Terms:
brain mapping, discrimination learning, form /pattern perception, imagery, neural information processing, neuron, neuropsychology, sensory discrimination, stimulus /response, visual perception
brain electrical activity, cell population study, experience, hippocampus, neuroregulation, prefrontal lobe /cortex, temporal lobe /cortex
Macaca mulatta, computer data analysis, electroencephalography, histology, magnetic resonance imaging, neuropsychological test, statistics /biometry

Institution: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
77 MASSACHUSETTS AVE
CAMBRIDGE, MA 02139
Fiscal Year: 2006
Department: PICOWER INSTITUTE FOR LEARNING AND MEMORY
Project Start: 01-APR-2002
Project End: 31-JAN-2007
ICD: NATIONAL INSTITUTE OF MENTAL HEALTH
IRG: IFCN

The Journal of Neurophysiology Vol. 88 No. 2 August 2002, pp. 929-941

Copyright 2002 by the American Physiological Society

Visual Categorization and the Primate Prefrontal Cortex: Neurophysiology and Behavior

David J. Freedman,1,2,5 Maximilian Riesenhuber,3,4,5 Tomaso Poggio,3,4,5 and Earl K. Miller1,2,5

1Center for Learning and Memory, 2The Institute of Physical and Chemical Research-Massachusetts Institute of Technology Neuroscience Research Center, 3Center for Biological and Computational Learning and 4McGovern Institute for Brain Research, 5Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

Subjects
Two female adult rhesus monkeys (Macacca mulatta) weighing 6.0 and 7.5 kg were used in this study. Using previously described methods (Miller et al. 1993 ), they were implanted with a head bolt to immobilize the head during recording and with recording chambers. Eye movements were monitored and stored using an infrared eye-tracking system (Iscan, Cambridge, MA). All surgeries were performed under sterile conditions while the animals were anesthetized with isoflurane. The animals received postoperative antibiotics and analgesics and were handled in accord with National Institutes of Health guidelines and the recommendations of the Massachusetts Institute of Technology Animal Care and Use Committee.

Recording techniques
Electrode penetration sites were determined using magnetic resonance imaging scans obtained prior to surgery. The recording chambers were positioned stereotactically over the lateral prefrontal cortex such that the principal sulcus and ventrolateral prefrontal cortex were readily accessible.

Behavioral tasks
The monkeys performed a delayed match-to-category task that required them to judge whether two successive stimuli were from the same category (Fig. 2). The trial began when the monkey grasped a metal bar and fixated a small (0.3) white spot at the center of a CRT screen. They were required to maintain gaze within a 2 square window around the fixation spot for the entire trial. After the initial 500 ms of fixation, a sample image was presented at the center of the screen for 600 ms, followed by a 1,000-ms delay. Then a choice image appeared. If the sample and choice stimuli were from the same category (a category match), the monkeys were required to release the lever before the stimulus disappeared 600 ms after its onset to receive a juice reward.  

Please email: EARL K. MILLER, ekmiller@mit.edu to protest the inhumane use of animals in this experiment. We would also love to know about your efforts with this cause: saen@saenonline.org

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Rats, mice, birds, amphibians and other animals have been excluded from coverage by the Animal Welfare Act. Therefore research facility reports do not include these animals. As a result of this situation, a blank report, or one with few animals listed, does not mean that a facility has not performed experiments on non-reportable animals. A blank form does mean that the facility in question has not used covered animals (primates, dogs, cats, rabbits, guinea pigs, hamsters, pigs, sheep, goats, etc.). Rats and mice alone are believed to comprise over 90% of the animals used in experimentation. Therefore the majority of animals used at research facilities are not even counted.

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